TheorySpark election games are by far the best programs I've played. They put you right in the seat as a candidate for quite a few offices (President, PM of Canada, PM of UK, Chancellor of Germany, PM of Aussie, Premier of British Columbia, etc.) and is very customizable. You can play as a real candidate, with preset ideological positions, or you can create your own. Hell, you can create your own party if you're that interested in modding. I really recommend it.

But... it isn't free, which is true for most good games of this caliber. If you want to have something worthwhile, you need to pay, and in honesty this isn't expensive - 14 Euros.